New compression options require pkg-config
Previously, tor only required pkg-config to build with systemd support. So only Linux distributions with systemd needed to worry about pkg-config.
Now the compression options also require pkg-config, making it a new dependency on a significant number of platforms.
We need to put this in the release announcement.
See: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=219864#c1